Such jacks are needed preferably to lift automobiles in the event of a breakdown in order to replace a defective wheel with a spare.
German AS 2 444 132 discloses such a jack. It has an upright leg and a supporting arm that pivots around a horizontal axis. The leg and the arm pivot toward each other subject to an activating mechanism that attaches directly to each. The leg and supporting arm in this jack are lengths of structural metal U section. The sides of both the leg and the arm section are secured to its base at a right angle, leaving a rather sharp edge.